Trampoline Questions ?

[RMH]

I have Open spectra nets on my Catana 48 which are fixed to each hull using stainless eye bolts which pass through a molded one and a half inch flange running fore and aft along each hull.

These eye bolts are mounted about 8 inches apart along each flange.
The tramp is fixed along each side using one continuous rope.

The odd eye bolt has individually ripped through the fibreglass flange and so I wondered two things.

1) If I strengthen the two flanges with additional woven roving and epoxy do you think I need the eye bolts at all or could I just drill holes through the fibreglass flanges and us the holes to tension the nets ?

Am I better to have individual lashings or a continuous lashing to secure the nets ?

My tramps are not really under much tension and sag because of that and although this isn't a problem for me I just wondered exactly how tight they should be ?

Thanks

Richard.

[Cotemar]

Maybe this will help.

1. Lashed with 3/16th. Each lashing is separate. Poor installations will simply use a single line along each side but this will fail in a short time.
Single lashings are much stronger.

2. The lashings are wrapped three times and then cinched tight. You tighten gradually and then go back and tighten again until the net is stretched to all four edges. A large fid helps to lock the lashing as it is tightened.

The job finished properly gives you tramps that will be very firm and will last a long time.

[RMH]

Thanks that's very helpful.
3/16 spectral ?

Do you think I can lash to holes drilled through the flange or do I have to use the eye bolts ?

[Cotemar]

Originally Posted by RMH

Thanks that's very helpful.
3/16 spectra ?

Do you think I can lash to holes drilled through the flange or do I have to use the eye bolts ?

If your going to use Amsteel / Spectra you can use 1/8" which has an Average Tensile Strength = 2,500 lbs

The 3/16",Amsteel / Spectra has an Average Tensile Strength: 5,400 lbs,

There are a few catamarans that have the tramps lashed through the fiberglass, so it will work.

[RMH]

That's really really helpful and thanks.
I cannot see why it's any worse to loop through an eye bolt that is bolted through the flange than looping straight through the hole that's already drilled through the flange for the eye bolt ?

[StuM]

Originally Posted by RMH

That's really really helpful and thanks.
I cannot see why it's any worse to loop through an eye bolt that is bolted through the flange than looping straight through the hole that's already drilled through the flange for the eye bolt ?

How sharp are the edges of the drilled holes compared to running around an eye?

[RMH]

Depends how much I round them off I suppose ?

[UNCIVILIZED]

Yep, there's the question as to how sharp the edges of the hole are, along with whether or not the holes are sufficiently large to allow multiple passes of line to fit through them.

Also, I know that Kurt Hughes spec'd one boat to have it's tramps secured via such holes in a composite, & that the builders hated him for it due to the immense amount of time required to construct, & properly bevel/round all of the holes for the lashings. Which, I'm not sure if he ever designed another boat with tramps secured this way or not. But on his personal boat there were U-bolts to which to affix the nets.

Oh, & individual lashings trump the 1-line method.

[RMH]

Yes thanks for that. I have a 2" horizontal flange along which there are eye bolts sticking up vertically. The existing continuous lashing goes through the eye bolts. I see no reason not to change this to individual lashing but if I lash them through the eye bolts they then exert pressure on the eye bolt which in fact twisted one of them completely through the flange.

I just want a solution that works and initially thought of keeping the eye bolts and just putting larger washers on them to spread the load but then I thought why have them at all ?

I am grateful for any and all suggestions to stop another eye bolt being pulled through this flange. I have attached a photograph to explain.

[RMH]

Photo

[UNCIVILIZED]

You can also put a plate underneath of the collar below the eye section of the bolt, before it goes through the flange, along with adding bigger washers (or plates) underneath of the nuts. It'll help to spread the compressive loads over a bigger area of the flange, just as washers do for nuts.

[RMH]

Thanks everyone that's a fantastic response and I really appreciate the advise.

Good stuff

Richard

[Brob2]

Who's allowed these miscreants to post in the mono-hull board?

Perhaps we could move this for future inquirers?

[Sos]

I would remove the eye bolts since lashing to them puts them in bending and therefore higher loads than if you lashed directly to the flange. A countersink drill bit should round the top and bottom edges .

[paxfish]

I have resolved that tramps are a necessary PITA, but that install with the eye bolts looks to be a an especially poor design.